It is widely known that UVA (320-400 nm) and UVB (280-320 nm) having a shorter wavelength than visible light may adversely affect skin. Thus, many studies have been conducted to develop an organic or inorganic blocking agent for blocking UVA and UVB.
In addition, IR occupies 80% of sunlight, is reflected or scattered by microparticles in the atmosphere to a lower degree as compared to UV or visible light, and transmits through the atmosphere to reach the ground while not being interrupted by molecules such as oxygen or nitrogen in the atmosphere. IR is known to stimulate blood circulation in a body and to provide a hyperthermic effect, but recent studies have revealed that IR is harmful to skin, and stimulates skin wrinkle formation, for example.
IR is classified, depending on the wavelength, into near-IR having a wavelength of 780-3000 nm, IR having a wavelength of 3000-25000 nm, and far-IR having a wavelength of 25000 nm or higher. Among those, the mechanism of skin wrinkle formation caused by near-IR is different from the known mechanism of skin wrinkle formation caused by UV. As a result, in the case of exposure to sunlight including UV simultaneously with near-IR, skin aging may be accelerated even when applying the existing UV blocking agent to skin.
Therefore, there is a need for a formulation for blocking out light over a wide range of wavelengths to screen skin from UV and near-IR simultaneously.